Drywall joint systems and method for making the same

ABSTRACT

A method for forming drywall joint systems wherein abutting edges of adjacent wallboard panels are adjoined by a thermoplastic adhesive substance which acquires its adhesive properties when heated and allowed to cool. The thermoplastic adhesive is applied to the joint formed by adjacent wallboard panels after they are erected or it is preapplied and then reheated after wallboard erection. Joint systems formed according to the method may consist of the thermoplastic adhesive substance alone or with other joint-forming materials such as jointreinforcing tape and/or a cementitious adhesive.

United States Patent [72] lnventors John D. Shull, Jr.;

Richard E. Smith, Tonawanda; Joseph W. Schneller, Williamsville; WilliamR. Burke, Tonawanda, N.Y.

[21 Appl. No. 844,306

[22] Filed July 24, 1969 [45] Patented Apr. 27, 1971 [73] AssigneeNational Gypsum Company Buffalo, N.Y.

[54] DRYWALL JOINT SYSTEMS AND METHOD FOR MAKINGTHESAME 17 Claims, 11Drawing Figs.

[52] U.S.Cl 52/309, 52/173,52/4l7, 52/746, 156/71, 156/275, 161/44 [51]lnt.Cl E041) 2/72 [50] FieldofSearch 52/127,

[56] References Cited UNITED STATES PATENTS 2,313,990 3/1943 Crandell52/417 2,392,734 1/1946 Haberstump 52/309X 2,922,200 1/1960 Atwood eta1. 52/309 2,995,784 8/ 1 961 Driscoll 52/ 309x 3,350,257 10/1967Hourigan etal. 52/309X 3,391,037 7/1968 McNulty 52/309X 3,432,375 3/1969161/44 3,444,657 5/1969 Swanson 52/417X FOREIGN PATENTS 1,026,223 4/1966Great Britain 156/275 Primary Examiner-Alfred C. Perham Att0rney-RobertF. Hause ABSTRACT: A method for forming drywall joint systems whereinabutting edges of adjacent wallboard panels are adjoined by athermoplastic adhesive substance which acquires its adhesive propertieswhen heated and allowed to cool. The thermoplastic adhesive is appliedto the joint formed by adjacent wallboard panels after they are erectedor it is preapplied and then reheated after wallboard erection. Jointsystems formed according to the method may consist of the thermoplasticadhesive substance alone or with other jointforming materials such asjoint-reinforcing tape and/or a cementitious adhesive.

PATENTEU APRZ'! l9?! sum 1 0P3 INVENTORS.

John D. Shull Jr. Richard E. SmHh Joseph W. Schneller R. Burke ATTORNEYPATENTEDAPRNIBYI 3.576091 sum 2 0F 3 V John D. Shull Jr.

44 Richard E. SmiNn Joseph W. Sichneller illiom R. Burke ATTORNEY IN VENTOR S.

Pmmmmzmn 3576091 SHEET 3 OF 3 INVENTORS.

John D.Shull Jr. Richard E. Smith Joseph W. Schneller William R. BurkeATTORNEY DRYWAILL rornr SYSTEMS AND METHOD FOR rune THE SAME BACKGROUNDOF THE DISCLOSURE Drywall construction commonly involves applying aplurality of wallboard panels to framing thus forming joints between theadjacent board panels. A common method of concealing these jointsconsists of adhering thereover a narrow paper joint tape by means of anaqueous cementitious adhesive. After the adhesive has been allowed todry for a period of about one day a thin layer of the cementitiousadhesive is smoothly applied thereover, it being somewhat wider than thepaper tape and tapered out to very thin edges. This second layer ofadhesive material is allowed to dry for about one day and another thinlayer of adhesive, somewhat wider, is applied thereover. In this mannera final substantially monolithic wall surface appearance is providedwhen the complete surface is covered with a decorative coating of paintor the like.

The paper tape provides reinforcing strength to the joint system,preventing cracking of the adhesive along the joint line. With thiscommon technique for concealing drywall joints there often develops aslight ridge or bead on the wall surface directly over the joint. Thisdefect can mar the monolithic appearance of the wall surface and costlyrepairs may be required to correct the condition. Moreover this methodof forming joint systems requires a relatively long period of time dueto the necessity of waiting about one day for each layer of adhesive todry before the next layer can be applied.

SUMMARY OF THE INVENTION The present invention relates to the use ofthermoplastic adhesive substances, commonly referred to as hot meltadhesives, to form joint systems between adjacent wallboard panels. Thethermoplastic adhesives may be employed alone or together with otherjoint-forming materials such as a strip of a joint-reinforcing tapeand/or a cementitious adhesive. These thermoplastic adhesive substancescan be conveniently applied by heating them to a temperature at whichthey acquire fluid properties and then spreading a layer thereof overthe joint. They return to the temperature at which they solidify veryquickly whereupon a decorative coating or an additional layer ofjoint-forming material can be immediately applied thereover. Jointsystems formed in accordance with the practice of the invention are atleast comparable in strength and quality with those made by the priorknown method with the advantage that they may be made in a significantlyshorter period of time.

It is an object of this invention to provide a novel method forconcealing drywall joints in simulated monolithic wall construction andfurther to provide a method requiring less time than was heretoforenecessary to form joints of a quality at least equal to those made bythe prior known methods. It is another object to provide such a methodwhich forms joints which have improved resistance to beading. It is afurther object to provide a simulated monolithic drywall surfaceincluding joints formed by the novel method.

Still another object is to provide novel wallboard panels which areadapted for forming the novel joint systems of the invention. It is yetanother object to provide a novel apparatus for applying thethermoplastic adhesive substances to drywall joints at a job site.

These and other objects and advantages of the present invention will bemore fully apparent when considered in relation to the preferredembodiments thereof as set forth in the specification and as shown inthe drawings in which:

FIG. I through FIG. 4 are perspective views of sections of simulatedmonolithic wall surfaces including drywall joint systems formed inaccordance with the invention.

FIG. 5 through FIG. 8 are end views of novel wallboard panelsmanufactured in accordance with the invention.

FIG. 9 represents, in purely diagrammatical fashion, a side view of anapparatus suitable for use in forming the joint systems of theinvention.

FIG. 10 is a perspective view of a preferred embodiment of thepositioning slide shoe of the apparatus shown in FIG. 9.

FIG. 11 is a perspective view of a preferred embodiment of the adhesivecontaining screed element of the apparatus shown in FIG. 9.

It should be understood that when reference is made herein to hot meltadhesives we mean thermoplastic substances which are composed of athermoplastic polymeric material and a diluent system. The hot meltadhesives may be generally defined as percent nonvolatile thermoplasticsubstances which exist in a solid form at room temperature and whichbecome sufficiently fluid or tacky at elevated temperatures to beemployed as adhesives.

The polymer is the essential ingredient in any hot melt adhesive system.Almost any thermoplastic polymeric material with adequate resistance toheat degradation can be suitable for incorporation into a hot meltadhesive. Examples of filmforming resins which are commonly used forthis purpose are polyethylene, polyvinyl acetate, ethylene-vinyl acetatecopolymers and the like. As the molecular weights of the polymersincrease it may be generally said that the viscosities, strengths andmechanical properties of the adhesive systems increase.

The diluent system, which is usually a blend of materials such as a wax,a plasticizer, a heat stabilizer and perhaps dyes, an inert filler or anextender, makes it. possible to utilize the properties of the polymer.The diluent functions as the vehicle for the polymer, lowering itsviscosity thus making it more convenient to apply as well as enhancingits wetting ability and adhesive strength.

According to the invention the hot melt adhesives are utilized as thebasis for various joint systems formed between adjacent drywall panelssuch as gypsum wallboard. In one commonly used form of gypsum wallboard,a generally rectangular panel, the front surfaces of the individualboard panels have a substantially flat central surface disposed betweenrecessed marginal surfaces of substantially greater width than depthextending in the longitudinal direction. The recessed marginal surfacestarts at a distance of from about 2 5m 3 inches from the panel edge andslopes downwardly to a maximum depth of from about 0.050 to about 0.070inch. The invention will be described in detail with respect to this.form of gypsum wallboard although it should be recognized that it may bepracticed with various types of drywall materials as well as with gypsumwallboard having differently shaped edges.

When these wallboard panels are erected in edgewise abuttingrelationship on framing, the abutting edges of adjacent panels thusdefine a shallow recessed area which extends on both sides of the joint.Subsequently this recessed area, which is commonly known within theindustry as the taper area, is filled with joint-concealing material.The particular joint system used must have a smooth, substantially flatouter surface which is substantially level with the central surfaces ofthe wallboard panels, somewhat wider than the taper area and whichtapers out to very thin edges. The novel joint systems of the inventioncan consist of only the hot melt adhesive or a base layer of thethermoplastic adhesive covered with one or more layers of anothersuitable joint-forming material. Narrow strips of joint-reinforcingmaterials may be embedded within the joint systems for added strengthwhere it is so desired. It is preferred to use paper joint tape or openmesh fiber cloths made from relatively strong material such as glassfiber to reinforce the drywall joints. The thermoplastic adhe sive ispreferably applied in a layer having a maximum thickness of from about0.010 to about 0.070 inch. The width of the layer can vary considerably,it being dependent upon factors such as the type of joint system formed,the method used to apply the thermoplastic adhesive to the joint and thetype of drywall as well as the shape of its edges as will be seenfurther below.

Referring to the drawings, FIG. I is a perspective view of a simulatedmonolithic wall construction including a joint made in accordance with apreferred embodiment of the invention. wallboard panels I and 12 areerected in a manner such that the recessed marginal surfaces thereof 14and I6 respectively define a taper area extending from line atransversely across the wall surface to line a. Disposed over the jointfonned between the abutting edges of the panels is a layer of a hot meltadhesive 18 which has a smooth, substantially flat outer surface 20. Thelayer of adhesive 18 is somewhat wider than the taper area and istapered out to very thin edges. The outer surface 20 of the adhesivelayer 18 is substantially level with the substantially flat centralsurfaces 22 and 24 of panels and 12 respectively thus providing anoverall wall surface which will give an attractive monolithic appearancewhen covered with a layer of a decorative coating composition.

FIG. 2 is a perspective view of a simulated monolithic wall constructionincluding a joint system formed in accordance with another preferredembodiment of the invention. A layer of a thermoplastic adhesive 26which covers about three-quarters of the surface of the taper area isapplied over the joint. A thin covering layer of an aqueous cementitiousadhesive 28, somewhat wider than the taper area is applied over the baselayer of thermoplastic adhesive 26. The cementitious adhesive layer 28is formed with a smooth substantially flat outer surface 30 which issubstantially level with the substantially flat central surfaces 22 and24 of wallboard panels I0 and I2 respectively.

FIG. 3 is illustrative of still another preferred embodiment of theinvention. This joint system consists of a base layer of a thermoplasticadhesive 32, a strip of paper joint tape 34 adhered thereover and havinga width substantially equal thereto, and a thin covering layer of acementitious adhesive 36 formed with the same characteristics describedwith respect to the layer of cementitious adhesive in FIG. 2.

FIG. 4 illustrates the same type of joint system described in FIG. 3with the exception that the joint-reinforcing material is an open meshfiber material 38 which is substantially encased within the layer ofthermoplastic adhesive 40.

The joint systems formed in accordance with the invention are capable ofbeing finished in a significantly shorter period of time than isrequired for those made with the prior known method. When the hot meltadhesives are heated to elevated temperatures sufficient to give themfluid propertiesin most cases 300 to 400 F-they can readily be appliedto drywall joints. These adhesives subsequently cool very rapidly thusreturning to a solid form in a period of about a minute or less. A layerof a decorative coating composition can then be immediately appliedthereover. Where it is desired to dispose a covering layer of anotherjoint-forming material, e.g. an aqueous cementitious adhesive, it is notnecessary to observe any extended waiting period before doing so. Thusthis novel method of fonning drywall joints eliminates the necessity ofwaiting about one day after the initial layer of adhesive has been laiddown before the next layer can be applied as has heretofore been thecase. This reduction in the time required to form joint systems can leadto significant economies for contractors in the building industry.Moreover, these novel joint systems have been shown to be of a qualityat least equal to those made by the prior known method. Strength testshave shown that joint systems employing the thermoplastic adhesivesperform favorably in comparison with those utilizing paper joint tapeembedded in an aqueous cementitious adhesive.

Another advantage of forming joint systems with the method of thepresent invention is that it is possible thereby to decrease thetendency of the joint to bead. Beading is a joint deformity whichappears as a line or ridge along the joint. Unfortunately when thiscondition occurs it is not apparent at the time the joint treatment iscompleted and may require several months to develop and manifest itself.When it does occur costly redecorating procedures may be necessary tocorrect the defect. This condition appears to be due to a number offactors all of which are not completely understood in view of thedifference of opinion which exists within the industry relative to thecause of the problem and methods for preventing its occurrence. It isgenerally agreed, however, that 5 moisture is one of the mostsignificant factors causative of this condition. With the joint systemsof the invention at least a substantial part of the wallboard surfacesin the joint area are covered with a hot melt adhesive most of which arehighly water resistant. By using a water-resistant thermoplasticadhesive the amount of water which could be absorbed by the wallboard inthe joint area is greatly diminished thus reducing the possibility ofbeading occurring.

Since the hot melt adhesives effect an instant bond with the drywallpanels these novel joint systems can be utilized to great advantage inindustrialized or prefabricated construction where complete wall surfaceassemblies are constructed at a manufacturing plant for later erectionat a building site. The thermoplastic adhesives, by effecting an instantbond, will rigidize the wall surface assembly sufficiently to allow itto be immediately moved within the plant or transported to the buildingsite. The ability to move these assemblies immediately after the jointsystem is formed can greatly increase the rate at which they can be madeby the manufacturer.

Various methods can be utilized to form drywall joints with hot meltadhesives. One such technique consists of coating the adhesive on thelongitudinal edges of the individual panels at the wallboardmanufacturing plant. The thermoplastic substance can conveniently beapplied to the panels by heating it to an elevated temperature at whichit becomes fluid and coating it on the appropriate edges as the panelsproceed along a continuous conveyor belt. When this applicationtechnique is employed it is preferred to cover the edge surfacecompletely with the adhesive.

FIG. 5, FIG. 6 and FIG. 7 are illustrative of some of the edgeformations which the wallboard panels could have and the manner in whicha layer of thermoplastic adhesive could be disposed thereover. These areend views of a section of the wallboard panels 42 which have a layer ofhot melt adhesive 44 adhered thereto. The panels can be erected at abuilding site by the procedures normally employed since it is possibleto drive a nail or a screw through the adhesive substance. When thepanels are erected the adhesive is then heated to cause it to becomesubstantially fluid thus enabling the adhesive layers on the adjacentpanel edges to flow together. An integral layer of the adhesive isformed over the joint when the adhesive cools.

A number of techniques may be utilized to heat the adhesive after thewallboard panels have been erected. Thin, high resistance electricalwires can be embedded in the adhesive layer as it is applied to thepanels at the wallboard manufacturing plant with the ends of the wiresbeing allowed to remain exposed. After erection of the panels theexposed wires can be connected to an electrical power source, eg a wetor dry cell battery, which is suitable to generate an electrical currentsufficient to cause the adhesive to become substantially fluid. Thetemperature of the adhesive can be quickly elevated to the levelnecessary to accomplish this result in this manner. After the integrallayer of adhesive has been formed over the joint the wires can be leftembedded in the adhesive layer with the exposed ends either removed orconcealed with a covering layer of another joint-forming material. It ispreferred to have about four to six wires for a layer of adhesive havinga width of one-half inch; however, the number of wires necessary and thecurrent required are dependent upon the particular hot melt adhesiveapplied to the panels. FIG. 8 is an end view of a section of a wallboardpanel 42 having the thin high resistance electrical wires 46 located inthe adhesive layer 44. The thermoplastic adhesive can also be heated toa substantially fluid fonn by means of a heat gun or by dielectricheating.

The hot melt adhesive can also be applied to a drywall joint after theindividual panels have been erected to form a wall surface. The adhesiveis heated to a fluid state and applied to the joint by means adapted toform a smooth layer thereof.

Some of the fluid substance will flow intothe area between the abuttingedge surfaces thus adding to the strength of the bond at the joint. Theextent to which the edge surfaces of the wallboard panels are coveredwith adhesive when this technique is used will be dependent upon factorssuch as the viscosity of the adhesive and how closely the adjacentpanels are positioned relative to each other. it should be recognized,however, that joint systems of high quality may be formed without anysubstantial part of the abutting edge surfaces being covered with theadhesive.

The hot melt adhesive may also be applied to a drywall joint byinitially adhering it to a strip of a joint-reinforcing material andutilizing the latter as a carrier for the adhesive. An integral unit canbe formed by adhering a layer of the adhesive to one side of thereinforcing material or by substantially encasing the latter in theadhesive. Where the joint-reinforcing material is a continuous web, eg apaper joint tape, or the like it is preferred to adhere a layer ofadhesive to one side of the material. When an open mesh fiber materialis used it may be substantially completely encased in a layer of theadhesive or only the strands of the material may be coated therewith.The combination of joint-reinforcing material and hot melt adhesive isheated to render the latter substantially tacky and then adhered to thewallboard surface over the joint.

FIG. 9 is a schematic representation of a preferred embodiment of anapparatus which is capable of efiiciently applying a layer of a hot meltadhesive to a drywall joint after the wallboard panels have been erectedat a building site. The apparatus is a standard hot melt adhesiveapplicator which has been specifically adapted for this purpose. The,basic applica' tor is available from the United Shoe Machinery Companyof Canada, Ltd. It should be understood that the novelty of theapparatus resides in the modifications made thereto.

The applicator $8 is electrically powered, having a cord 50 which can beconnected into any standard electrical outlet and is activated by meansof a trigger 52. The thermoplastic adhesive is fed into the applicatorin the form of a cylindrical cord 54, advanced forwardly through anadhesive guide tube 56 into a melt body 58 where it is heated to anelevated temperature and exits from the apparatus as a fluid through anozzle 6th. The handle 62 of the applicator has pivotally attachedthereto a positioning sliding shoe M by means of a connecting pin 66which allows the applicator to be rotated over an arc of about 90 in aplane perpendicular to that of the positioning sliding shoe 64. A screedelement 68 which is formed so as to also define an adhesive reservoirarea is fitted on to the applicator extending forwardly of the nozzle60. The screed element on has opposite sides adjoined at a centralportion and a bottom edge 70 which is adapted to lie in a plane commonwith the bottom plane of the sliding shoe when the apparatus is inoperative position.

The positioning sliding shoe 64 is adapted to move smoothly over asubstantially flat surface. It is held against the wall surface acrossthe joint positioning the applicator parallel with the direction of thejoint. The applicator is rotated forward until the bottom edge 70 of thescreed element 68 contacts the wall surface. initially an amount offluid adhesive sufficient to substantially fill the adhesive reservoirarea is allowed to exit from the nozzle while the applicator remainsstationary. lt is necessary to maintain the adhesive reservoir areasubstantially filled with fluid adhesive as the apparatus is being movedalong the joint in order to ensure a flow sufficient to form asubstantially uniform layer of the adhesive over the length of thejoint. The screed element is preferably metal and is attached to theapparatus in a manner such that it becomes heated when the apparatus isactivated thus preventing the fluid adhesive from solidifying before itcan be applied to the joint. The dimensions of the layer of adhesivedisposed over the joint by the apparatus are controlled by the width ofthe bottom edge of the screed element and the angle at which it contactsthe wall surface.

FIG. ll) is an elevated perspective view of a preferred embodiment ofthe positioning sliding shoe 64. H6. 11 is a perspective view of apreferred embodiment of the screed element 68 showing the bottom edgethereof 70 and the opposite sides 72 and 74 thereof.

Numerous hot melt adhesives are commercially available at the presenttime. These substances can have greatly varying viscosities, meltingtemperatures, bonding strengths, setting times, etc. It must be left tothe practitioner to determine which particular adhesive would be bestsuited for a specific application with regard to the type of wallboard,the method of application and various other considerations which arereadily apparent to those skilled in the art. The method of theinvention allows the formation of drywall joint systems of high qualityin significantly shorter periods of time than were necessary with theprior known method thus enabling those engaged in the field of simulatedmonolithic wall construction to achieve substantial economies.

Having given a detailed description of the preferred embodiments of theinvention so that those skilled in the art may practice the same wecontemplate that variations may be made therein.

We claim:

1. In simulated monolithic wall construction the method of concealingthe joints formed between adjacent wallboard panels comprising the stepsof:

a. heating a solid thermoplastic adhesive comprising a thermoplasticpolymer to an elevated temperature whereat it has fluid properties,

. applying said fluid adhesive to a wall surface formed by at least twowallboard panels erected in substantially edge abutting relationship,said panels each having an outer face surface arranged in substantiallycoplanar relationship with each other and an abutting edge surface whichis substantially perpendicular to said outer face surface, with saidadhesive adjoining at least the portion of each of the abutting edgesurfaces of said wallboard panels immediately adjacent the respectiveouter face surfaces thereof, and

c. cooling said thermoplastic adhesive to ambient temperature therebyreturning it to a solid form whereby a rigid unitary structure resistantto displacement or distortion otherwise caused by external effects isformed.

2. The method as defined in claim 1 wherein the fluid adhesive appliedto the wall surface is in the form of a layer con tacting at least theportion of said outer face surfaces of said wallboard panels immediatelyadjacent to the abutting edge surfaces thereof, said'layer having asmooth substantially flat outer surface and tapering out to thin edges.

3. in simulated monolithic wall construction the method of concealingthe joints formed between adjacent wallboard panels comprising the stepsof:

a. heating a solid thermoplastic adhesive comprising a thermoplasticpolymer to an elevated temperature whereat it has fluid properties,

b. applying said fluid adhesive to a wall surface formed by at least twowallboard panels erected in substantially edge abutting relationship,said panels each having an outer face surface arranged in substantiallycoplanar relationship with each other and an abutting edge surface whichis substantially perpendicular to said outer face surface, with saidfluid adhesive adjoining at least the portion of each of the abuttingedge surfaces of said wallboard panels immediately adjacent therespective outer surfaces thereof,

c. cooling said thermoplastic adhesive to ambient temperature therebyreturning it to a solid form d. disposing thereover at least one layerof an aqueous cementitious adhesive comprising a minor amount of bindermaterial, a major amount of inorganic filler material and a quantity ofwater sufficient to form a pastelike mixture of workable consistency,each layer of said cementitious adhesive being wider than the layer ofthermoplastic adhesive or cementitious adhesive immediately beneath it4. The method as defined in claim 3 wherein the fluid adhe sive appliedto the wall surface is in the form of a layer con tacting at least theportion of said outer face surfaces of said wallboard panels immediatelyadjacent to the abutting edge surfaces thereof, said layer having asmooth, substantially flat outer surface and tapering out to thin edges.

5. ln simulated monolithic wall construction the method of concealingthe joints formed between adjacent wallboard panels comprising the stepsof:

a. heating a narrow strip of joint-reinforcing tape having adheredthereto a solid thermoplastic adhesive comprising a then'noplasticpolymer to an elevated temperature whereat said adhesive becomessubstantially tacky, applying said strip of tape to a wall surfaceformed by at least two wallboard panels erected in substantially edgeabutting relationship, said panels each having an outer face surfacearranged in substantially coplanar relationship with each other and anabutting edge surface which is substantially perpendicular to said outerface surface with said tape adjoining at least the portion of said facesurfaces of said panels immediately adjacent said abutting edges thereofand said thermoplastic adhesive contacting said portion of the outersurfaces of said panels, and c. cooling said strip of tape and saidthermoplastic adhesive to ambient temperature thereby returning theadhesive to a solid form whereby a rigid unitary structure resistant todisplacement or distortion otherwise caused by external effects isformed.

6. in simulated monolithic wall surface construction the method ofconcealing the joints fonned between adjacent wallboard panelscomprising the steps of:

a. heating a narrow strip of joint-reinforcing tape having adheredthereto a solid thermoplastic adhesive comprising a thennoplasticpolymer to an elevated temperature whereat said adhesive becomessubstantially tacky, applying said strip of tape to a wall surfacefonned by at least two wallboard panels erected in substantially edgeabutting relationship, said panels each having an outer face surfacearranged in substantially coplanar relationship with each other and anabutting edge surface which is substantially perpendicular to said outerface surface with said tape adjoining at least the portion of said facesurfaces of said panels immediately adjacent said abutting edges thereofand said thermoplastic adhesive contacting said portion of the outersurfaces of said panels,

0. cooling said strip of joint-reinforcing tape and said thermoplasticadhesive to ambient temperature thereby returning the adhesive to asolid form,

d. disposing thereover at least one layer of an aqueous cementitiousadhesive comprising a minor amount of binder material, a major amount ofinorganic filler material and a quantity of water sufficient to form apastelike mixture of workable consistency, each layer of saidcementitious adhesive being wider than the strip of tape or layer ofcementitious adhesive immediately beneath it and having a smoothsubstantially flat outer surface tapering out to thin edges, and

e. drying each layer of said cementitious adhesive before a succeedinglayer is laid down thereover whereby a rigid unitary structure resistantto displacement or distortion otherwise caused by external effects isformed.

7. The method as defined in claim 6 in which said joint-reinforcing tapeis a paper tape.

8. A simulated monolithic wall comprising at least two wallboard panelserected in substantially edge abutting relationship forming a jointtherebetween, said panels each having an outer face surface arranged insubstantially coplanar relationship with each other and an abutting edgesurface which is substantially perpendicular to said outer face surfaceand at least the portion of said abutting edge surfaces of said panelsimmediately adjacent said face surfaces thereof being adjoinedthroughout the extent of the joint by a set thermoplastic adhesiveadhered to said portion of said edge surfaces, said set thermoplasticadhesive forming with said panels a rigid unitary structure resistant todisplacement or distortion otherwise caused by external effects.

9. A simulated monolithic wall as defined in claim 8 whereinsubstantially the complete abutting edge surfaces of the adjacent panelsare adjoined throughout the extent of the joint by said setthermoplastic adhesive.

10. A simulated monolithic wall as defined in claim 8 wherein said setthermoplastic adhesive is adhered to the portion of the respectivesubstantially coplanar outer face surfaces of said panels at leastimmediately adjacent the abutting edge surfaces of said wallboardpanels.

11. A simulated monolithic wall as defined in claim 9 wherein said setthermoplastic adhesive is adhered to the portion of the respectivesubstantially coplanar outer face surfaces of said panels at leastimmediately adjacent the abutting edge surfaces of said wallboardpanels.

12. A simulated monolithic wall comprising at least two wallboard panelserected in substantially edge abutting relationship forming a jointtherebetween, said panels each having an outer face surface arranged insubstantially coplanar relationship with each other and an abutting edgesurface which is substantially perpendicular to said outer face surface,at least the portion of said abutting edge surfaces of said panelsimmediately adjacent said face surfaces thereof being adjoinedthroughout the extent of the joint by a set thermoplastic adhesiveadhered to said portion of said edge surfaces, and at least one layer ofa hardened cementitious adhesive comprising a minor amount of bindermaterial and a major amount of inorganic filler material disposed oversaid thermoplastic adhesive, each layer of said cementitious adhesivebeing wider than the thermoplastic adhesive or cementitious adhesiveimmediately beneath it, said set thermoplastic adhesive and saidhardened cementitious adhesive forming with said panels a rigid unitarystructure resistant to displacement or distortion otherwise caused byexternal effects.

13. A simulated monolithic wall as defined in claim 12 whereinsubstantially the complete abutting edge surfaces of the adjacent panelsare adjoined throughout the extent of the joint by said setthermoplastic adhesive.

14. A simulated monolithic wall surface as defined in claim 12 whereinsaid set thermoplastic adhesive is adhered to the portion of therespective substantially coplanar outer face surfaces of said panels atleast immediately adjacent the abutting edge surfaces of said wallboardpanels.

15. A simulated monolithic wall as defined in claim 13 wherein said setthermoplastic adhesive is adhered to the portion of the respectivesubstantially coplanar outer face surfaces of said panels at leastimmediately adjacent the abutting edge surfaces of said wallboardpanels.

16. A simulated monolithic wall comprising at least two wallboard panelserected in substantially edge abutting relationship forming a jointtherebetween, said panels each having an outer face surface arranged insubstantially coplanar relationship with each other and an abutting edgesurface which is substantially perpendicular to said outer face surface,and a strip of joint-reinforcing tape having a set thennoplasticadhesive adhered thereto adjoining the portion of the outer face surfaceof the respective panels at least immediately adjacent said abuttingedge surfaces thereof with said set thermoplastic adhesive contactingsaid portions of the outer face surfaces of said panels, said setthermoplastic adhesive and said joint-reinforcing tape forming with saidpanels a rigid unitary structure resistant to displacement or distortionotherwise caused by external effects.

17. A simulated monolithic wall comprising at least two wallboard panelserected in substantially edge abutting relationship forming a jointtherebetween, said panels each having an outer face surface arranged insubstantially coplanar relationship with each other and an abutting edgesurface which is substantially perpendicular to said outer face surface,a strip of joint-reinforcing tape having a set thermoplastic adhesiveadhered thereto adjoining the portion of the outer face surface of therespective panels at least immediately adjacent the abutting edgesurfaces thereof with said set thermoplastic adhesive contacting saidportions of the outer face surfaces of said panels and at least onelayer of a hardened cementitious adhesive comprising a minor amount ofbinder material and a major amount of inorganic filler material, each ofsaid layers of said cementitious adhesive being wider than said strip ofjoint-reinforcing tape or layer of cementitious adhesive immediatelybeneath it, said set thermoplastic adhesive, said joint-reinforcing tapeand said hardened cementitious adhesive forming with said wallboardpanels a rigid unitary structure resistant to displacement or distortionotherwise caused by external effects.

2. The method as defined in claim 1 wherein the fluid adhesive appliedto the wall surface is in the form of a layer contacting at least theportion of said outer face surfaces of said wallboard panels immediatelyadjacent to the abutting edge surfaces thereof, said layer having asmooth substantially flat outer surface and tapering out to thin edges.3. In simulated monolithic wall construction the method of concealingthe joints formed between adjacent wallboard panels comprising the stepsof: a. heating a solid thermoplastic adhesive comprising a thermoplasticpolymer to an elevated temperature whereat it has fluid properties, b.applying said fluid adhesive to a wall surface formed by at least twowallboard panels erected in substantially edge abutting relationship,said panels each having an outer face surface arranged in substantiallycoplanar relationship with each other and an abutting edge surface whichis substantially perpendicular to said outer face surface, with saidfluid adhesive adjoining at least the portion of each of the abuttingedge surfaces of said wallboard panels immediately adjacent therespective outer surfaces thereof, c. cooling said thermoplasticadhesive to ambient temperature thereby returning it to a solid form d.disposing thereover at least one layer of an aqueous cementitiousadhesive comprising a minor amount of binder material, a major amount ofinorganic filler material and a quantity of water sufficient to form apastelike mixture of workable consistency, each layer of saidcementitious adhesive being wider than the layer of thermoplasticadhesive or cementitious adhesive immediately beneath it and having asmooth substantially flat outer surface tapering out to thin edges, ande. drying each layer of said cementitious adhesive before a succeedinglayer is laid down thereover whereby a rigid unitary structure resistantto displacement or distortion otherwise caused by external effects isformed.
 4. The method as defined in claim 3 wherein the fluid adhesiveapplied to the wall surface is in the form of a layer contacting atleast the portion of said outer face surfaces of said wallboard panelsimmediately adjacent to the abutting edge surfaces thereof, said layerhaving a smooth, substantially flat outer surface and tapering out tothin edges.
 5. In simulated monolithic wall construction the method ofconcealing the joints formed between adjacent wallboard panelscomprising the steps of: a. heating a narrow strip of joint-reinforcingtape having adhered thereto a solid thermoplastic adhesive comprising athermoplastic polymer to an elevated temperature whereat said adhesivebecomes substantially tacky, b. applying said strip of tape to a wallsurface formed by at least two wallboard panels erected in substantiallyedge abutting relationship, said panels each having an outer facesurface arranged in substantially coplanar relationship with each otherand an abutting edge surface which is substantially perpendicular tosaid outer face surface with said tape adjoining at least the portion ofsaid face surfaces of said panels immediately adJacent said abuttingedges thereof and said thermoplastic adhesive contacting said portion ofthe outer surfaces of said panels, and c. cooling said strip of tape andsaid thermoplastic adhesive to ambient temperature thereby returning theadhesive to a solid form whereby a rigid unitary structure resistant todisplacement or distortion otherwise caused by external effects isformed.
 6. In simulated monolithic wall surface construction the methodof concealing the joints formed between adjacent wallboard panelscomprising the steps of: a. heating a narrow strip of joint-reinforcingtape having adhered thereto a solid thermoplastic adhesive comprising athermoplastic polymer to an elevated temperature whereat said adhesivebecomes substantially tacky, b. applying said strip of tape to a wallsurface formed by at least two wallboard panels erected in substantiallyedge abutting relationship, said panels each having an outer facesurface arranged in substantially coplanar relationship with each otherand an abutting edge surface which is substantially perpendicular tosaid outer face surface with said tape adjoining at least the portion ofsaid face surfaces of said panels immediately adjacent said abuttingedges thereof and said thermoplastic adhesive contacting said portion ofthe outer surfaces of said panels, c. cooling said strip ofjoint-reinforcing tape and said thermoplastic adhesive to ambienttemperature thereby returning the adhesive to a solid form, d. disposingthereover at least one layer of an aqueous cementitious adhesivecomprising a minor amount of binder material, a major amount ofinorganic filler material and a quantity of water sufficient to form apastelike mixture of workable consistency, each layer of saidcementitious adhesive being wider than the strip of tape or layer ofcementitious adhesive immediately beneath it and having a smoothsubstantially flat outer surface tapering out to thin edges, and e.drying each layer of said cementitious adhesive before a succeedinglayer is laid down thereover whereby a rigid unitary structure resistantto displacement or distortion otherwise caused by external effects isformed.
 7. The method as defined in claim 6 in which saidjoint-reinforcing tape is a paper tape.
 8. A simulated monolithic wallcomprising at least two wallboard panels erected in substantially edgeabutting relationship forming a joint therebetween, said panels eachhaving an outer face surface arranged in substantially coplanarrelationship with each other and an abutting edge surface which issubstantially perpendicular to said outer face surface and at least theportion of said abutting edge surfaces of said panels immediatelyadjacent said face surfaces thereof being adjoined throughout the extentof the joint by a set thermoplastic adhesive adhered to said portion ofsaid edge surfaces, said set thermoplastic adhesive forming with saidpanels a rigid unitary structure resistant to displacement or distortionotherwise caused by external effects.
 9. A simulated monolithic wall asdefined in claim 8 wherein substantially the complete abutting edgesurfaces of the adjacent panels are adjoined throughout the extent ofthe joint by said set thermoplastic adhesive.
 10. A simulated monolithicwall as defined in claim 8 wherein said set thermoplastic adhesive isadhered to the portion of the respective substantially coplanar outerface surfaces of said panels at least immediately adjacent the abuttingedge surfaces of said wallboard panels.
 11. A simulated monolithic wallas defined in claim 9 wherein said set thermoplastic adhesive is adheredto the portion of the respective substantially coplanar outer facesurfaces of said panels at least immediately adjacent the abutting edgesurfaces of said wallboard panels.
 12. A simulated monolithic wallcomprising at least two wallboard panels erected in substantially edgeabutting relationship forming a joint therebetween, said panels eachhavinG an outer face surface arranged in substantially coplanarrelationship with each other and an abutting edge surface which issubstantially perpendicular to said outer face surface, at least theportion of said abutting edge surfaces of said panels immediatelyadjacent said face surfaces thereof being adjoined throughout the extentof the joint by a set thermoplastic adhesive adhered to said portion ofsaid edge surfaces, and at least one layer of a hardened cementitiousadhesive comprising a minor amount of binder material and a major amountof inorganic filler material disposed over said thermoplastic adhesive,each layer of said cementitious adhesive being wider than thethermoplastic adhesive or cementitious adhesive immediately beneath it,said set thermoplastic adhesive and said hardened cementitious adhesiveforming with said panels a rigid unitary structure resistant todisplacement or distortion otherwise caused by external effects.
 13. Asimulated monolithic wall as defined in claim 12 wherein substantiallythe complete abutting edge surfaces of the adjacent panels are adjoinedthroughout the extent of the joint by said set thermoplastic adhesive.14. A simulated monolithic wall surface as defined in claim 12 whereinsaid set thermoplastic adhesive is adhered to the portion of therespective substantially coplanar outer face surfaces of said panels atleast immediately adjacent the abutting edge surfaces of said wallboardpanels.
 15. A simulated monolithic wall as defined in claim 13 whereinsaid set thermoplastic adhesive is adhered to the portion of therespective substantially coplanar outer face surfaces of said panels atleast immediately adjacent the abutting edge surfaces of said wallboardpanels.
 16. A simulated monolithic wall comprising at least twowallboard panels erected in substantially edge abutting relationshipforming a joint therebetween, said panels each having an outer facesurface arranged in substantially coplanar relationship with each otherand an abutting edge surface which is substantially perpendicular tosaid outer face surface, and a strip of joint-reinforcing tape having aset thermoplastic adhesive adhered thereto adjoining the portion of theouter face surface of the respective panels at least immediatelyadjacent said abutting edge surfaces thereof with said set thermoplasticadhesive contacting said portions of the outer face surfaces of saidpanels, said set thermoplastic adhesive and said joint-reinforcing tapeforming with said panels a rigid unitary structure resistant todisplacement or distortion otherwise caused by external effects.
 17. Asimulated monolithic wall comprising at least two wallboard panelserected in substantially edge abutting relationship forming a jointtherebetween, said panels each having an outer face surface arranged insubstantially coplanar relationship with each other and an abutting edgesurface which is substantially perpendicular to said outer face surface,a strip of joint-reinforcing tape having a set thermoplastic adhesiveadhered thereto adjoining the portion of the outer face surface of therespective panels at least immediately adjacent the abutting edgesurfaces thereof with said set thermoplastic adhesive contacting saidportions of the outer face surfaces of said panels and at least onelayer of a hardened cementitious adhesive comprising a minor amount ofbinder material and a major amount of inorganic filler material, each ofsaid layers of said cementitious adhesive being wider than said strip ofjoint-reinforcing tape or layer of cementitious adhesive immediatelybeneath it, said set thermoplastic adhesive, said joint-reinforcing tapeand said hardened cementitious adhesive forming with said wallboardpanels a rigid unitary structure resistant to displacement or distortionotherwise caused by external effects.